1. Field of the Invention
The present invention relates to a paint composition which contains a silicone resin, a polytetrafluoroethylene polymer, and a polyurethane polymer in combination. The paint composition is useful as a surface coating that can be repeatedly cleaned with strong solvents and which possesses a non-stick surface.
2. The Prior Art
In large metropolitan areas, such as urban centers, equipment that is constantly used by the general public, such as telephones, are sometimes vandalized by being sprayed with chemicals and discolored with graffiti. This vandalism not only causes the appearance of the equipment to be undesirable, due to vulgarity, but also the chemicals used by the vandals may be harmful to those members of the public that may touch and use the equipment.
In addition there are other situations wherein undesirable self-stick labels are applied to surfaces of the equipment. During the time these labels are present on the surface, graffiti may be also written on blank portions of the label.
Attempts have been made in the past to overcome these problems. Prior proposed solutions are as follows.
It was desired to provide a paint formulation that could be repeatedly cleaned and from which self-stick labels could be readily removed.
Thus, many combinations of ingredients were prepared to develop this type of surface but to no avail. For example, attempts to develop a non-stick surface were by adding silicone alone to the paint. Many different types of silicones were tested, but it was found that the silicones detracted from the properties of the paint, without giving a non-stick surface, or the paint had a very oily surface that was completely unacceptable.
Then it was decided to add to the paint, tiny plastic particles such as "Hercuflat" brand polypropylene beads. This made the paint surface very bumpy and easy to scratch. Also it was decided to add flourocarbons ("Teflon") to the paint. This gave a non-stick surface, but the paint was very easily removed and scratched off. It is known that "Konar 500" process uses fluorocarbons a paint process, and then bakes the paint at very high temperatures to cause the fluorocarbon to melt and to reharden as part of the paint. This prior art process is unsuitable because it is desired to paint plastic parts, rather than metal parts. Many plastic parts would themselves melt at temperatures high enough to melt the fluorocarbon. It was desired to develop an air drying paint system that could be used on a production line at room temperature and drying in a few minutes for easy handling purposes.